The present description relates to a method for determining the vertical acceleration, the longitudinal angular acceleration and the lateral angular acceleration of a body. The body may be, in particular, a motor vehicle. The description further relates to a wheel suspension system and to a motor vehicle.
In order to reduce the susceptibility of technical equipment to degradation it may desirable that a technical function can be performed with a number of components as small as possible. For example, a motor vehicle, in particular the wheel suspension system of a motor vehicle, typically includes a multiplicity of sensors. These are, inter alia, sensors for measuring the vertical acceleration of the motor vehicle, sensors for determining the horizontal acceleration of the motor vehicle and distance sensors. Typically, four sensors for measuring the distance of the body with respect to the chassis components attached to the wheels, three accelerometers for determining the vertical acceleration of the motor vehicle and at least two accelerometers for determining the horizontal acceleration of the motor vehicle are used to determine the vertical acceleration, the longitudinal angular acceleration and the lateral angular acceleration of the motor vehicle.
Determination of the vertical acceleration, the longitudinal angular acceleration and the lateral angular acceleration at the center of gravity of the motor vehicle is of particular importance in connection with optimum control of the properties of the vehicle, especially control of the parameters of semi-active or active shock absorbers.
The design of the system for damping oscillations of the wheel suspension always represents a compromise between, on the one hand, screening the vehicle body from high-frequency oscillations (secondary ride) of the kind produced by road surface irregularities and, on the other, achieving a high level of driving comfort with regard to low-frequency oscillations of the vehicle body (primary ride). This means that, on the one hand, the vehicle body must be screened from high-frequency oscillations while on the other hand adequate control of the vehicle by the driver must thereby be assured, so that the driver receives feedback regarding the state of the vehicle and the road conditions.
Semi-active and active shock absorber systems can offer good screening from high frequencies generated by road surface irregularities while at the same time ensuring good control of the vehicle by the driver. In addition, the vehicle body can at the same time be screened from low frequencies produced by road surface irregularities.
Active damping systems have the disadvantage, as compared to passive damping systems, that they are considerably more complex and cost-intensive. In addition to the greater complexity of the hardware of the damper and the wheel suspension, as compared to conventional passive damping and wheel suspension systems, further sensors for executing the control and regulation algorithms of semi-active and active damping and wheel suspension systems are also required.
With regard to semi-active and active damping systems, the dynamics of the motion of the vehicle body are usually controlled with respect to low-frequency oscillations (primary ride). In the case of active damping systems, this is achieved by controlling the damping forces between the vehicle body and the four wheels. Variation of the damping forces is effected by the use of continuously adjustable shock absorbers.
In order to estimate the motion of the vehicle body, in particular in the context of active damping systems, three acceleration sensors fastened to the vehicle body are normally used. The measurement data of the acceleration sensors is used for calculating the accelerations of the vehicle body with respect to lift (heave) acceleration or vertical acceleration, roll acceleration or longitudinal angular acceleration, and pitch acceleration or lateral angular acceleration. In addition, the measurement data is integrated in order to determine the corresponding velocities. Additionally, the vertical deflections of the respective spring elements at the four corners of the vehicle are measured.
The inventors herein have recognized the above-mentioned disadvantages of cost and complexity and have developed a method for operating a vehicle, comprising: adjusting a damper in response to a vertical acceleration, a longitudinal angular acceleration, and a lateral angular acceleration provided via a mass of a vehicle body, two moments of inertia of the vehicle body, positions of a plurality of shock absorbers relative to a center of gravity of the vehicle body, a mean height of a longitudinal axis of rotation of the vehicle body, a mean height of a transverse axis of rotation of the vehicle body, damping forces of the plurality of shock absorbers, and spring forces of a plurality of spring elements coupled to the vehicle body.
By calculating the vertical acceleration, longitudinal angular acceleration, and lateral angular acceleration from the positions of a plurality of shock absorbers, the damping forces of the plurality of shock absorbers, vehicle inertia, and spring forces it may be possible to eliminate three axis accelerometers for controlling the suspension of a vehicle. Eliminating accelerometers can reduce system cost and lower the possibility of system degradation since fewer components may be used to control the vehicle suspension.
The present description may provide several advantages. Specifically, the approach may reduce system cost by reducing the number of system components. Further, a lower number of system components may reduce the possibility of system degradation since fewer components are relied upon to operate the system. Further still, the approach may allow for easier installation of the system to a vehicle since fewer components have to be installed to the vehicle.
The above advantages and other advantages, and features of the present description will be readily apparent from the following Detailed Description when taken alone or in connection with the accompanying drawings.
It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure.